introspection: Filter out private headers
introspection: Filter out private headers

We shouldn't scan private headers.  Also add --warn-all.

https://bugzilla.gnome.org/show_bug.cgi?id=627973

Distrotech/pango,danny-ku/pango,danny-ku/pango,kari-lentz/alpha-pango,Distrotech/pango,danny-ku/pango,kari-lentz/alpha-pango,Distrotech/pango,kari-lentz/alpha-pango,kari-lentz/alpha-pango